The present invention relates to an improvement in the process for the manufacture of viscose from a cellulose raw material. It is well known that the preparation of the spinning or casting solution of viscose in the manufacture of rayon or cellophane is conventionally effected by steeping the cellulose in caustic soda, expressing the excess caustic, shredding and aging the resulting alkali cellulose to a desired molecular size, reacting the aged alkali cellulose with carbon disulfide to form cellulose xanthate, and dissolving the latter in dilute caustic soda to form a viscose solution. This solution is aged or ripened and filtered prior to spinning or casting into a film.
The properties of the final product depend upon a number of different factors. One important factor is the ripening of the viscose.
The process of viscose aging involves a spontaneous breaking down of some of the xanthate sulfur linkages, resulting in a lower xanthate sulfur content, a lower solubility of the cellulosic material and easier coagulability.
If the degree of ripening is not kept constant, then the properties of the resultant fiber or fibers will vary widely. In fact, if the chemical age is far from specification, the coagulation properties of the viscose may be incompatible with the particular spinning conditions being used, and the viscose may not spin at all.
In conventional practice the determination of the proper chemical age or degree of ripeness is done by periodically testing samples by either a salt test for determining its coagulability or by a chemical analysis of xanthate and the total sulfur content of the viscose.